This invention relates to adsorbent enclosures, and more specifically, to an adsorbent enclosure for an automatic tissue processor to filter the toxic fumes produced by the tissue processor during operation.
A pathologist's diagnosis is based upon light microscopy examination of slides of wax penetrated tissues which have been microtomed and stained. Electron microscopy examination requires similar specimen treatment with fixation, dehydration and clearing solvents, but the embedding media is a polymer rather than wax. Companies such as Technicon, Lipshaw, Tissue-Tek, American Optical, and Fisher manufacture automatic tissue processors which sequentially immerse specimens into a plurality of solvent baths. In order to be penetrated with wax, a typical sequence of solvents used on specimens in a tissue processor consists of formalin (an aqueous solution of formaldehyde), isopropyl alcohol and xylene.
Formaldehyde, xylene and isopropyl alcohol vapors which emanate from automatic tissue processors are toxic and thus controlled by OSHA (Occupational Safety and Health Act). The TLV (Threshold Limit Value), the time weighted average concentration a worker can be exposed to in an eight-hour day for formaldehyde is 3 ppm (parts per million), xylene is 100 ppm, and isopropyl alcohol is 400 ppm. Interim toxicological findings indicate that formaldehyde is a suspect carcinogen. Ventilation systems are very expensive especially in retrofitting an old laboratory and in addition cause high energy loss by the discharge of warm room air and result in governmental regulation of the points of emission.
The present invention relates to an improved adsorbent enclosure for treating the toxic vapor emanating by a tissue processor and more particularly to a framework which supports the adsorbent/exhauster blower and a clear flexible impermeable cover with provision for access during operation and maintenance. The volume exhausted from the enclosure is maintained to yield low solvent evaporation from the tissue processor's solvent baths, but with minimal risk of an explosion. The volume exhausted is balanced between high solvent evaporation at high volumetric rates and the potential for an explosion at low volumetric rates.
By way of background, the U.S. Pat. No. 2,624,333 discloses an incubator having a frame which mounts a plastic tent with zippers for access. No fasteners are used to keep the panels open during loading. No space between the tent and frame is provided for inlet air. Oxygen is supplied to the recirculated and treated air within the incubator. The incubator/framework disclosed in U.S. Pat. No. 2,624,333 does not relate to tissue processors.
By way of further background, U.S. Pat. No. 3,492,987 discloses an isolation apparatus including a tent mounted on a frame carried by a bed. A U-form slide extends around the side and bottom of one side of the enclosure to permit access to the patient. The bottom of the tent-like enclosure is sealed to the bed frame. Canisters connected by conduits to the enclosure clean contaminated air from the enclosure before passing into the room. Air is forced into the enclosure by a pump located elsewhere. The patent does not disclose a space between the bottom of the enclosure and a table or the like for permitting entry of room air, nor are flaps bordered by separate vertical zippers to permit access to the inside of the tent shown. The isolation apparatus disclosed in U.S. Pat. No. 3,492,987 does not relate to tissue processors.